Differentiate between ‘nuclear fission’ and ‘nuclear fusion’. Briefly discuss one example of each.
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Nuclear fission releases energy by splitting heavy nuclei, while nuclear fusion releases energy by combining light nuclei. Fusion has higher energy yield but is harder to achieve under controlled conditions.
(a) Difference between Nuclear Fission and Nuclear Fusion: Nuclear Fission: Nuclear fission is the process where a heavy atomic nucleus, like uranium-235, splits into two lighter nuclei. This splitting releases a significant amount of energy. It is typically initiated by the absorption of a neutron. Fission generally produces fission fragments and free neutrons. Example: The energy released from the fission of uranium-235 in a nuclear reactor.
Nuclear Fusion: Nuclear fusion is the process where two light atomic nuclei, such as hydrogen isotopes, merge to form a heavier nucleus, releasing energy. This process occurs naturally in celestial bodies like stars, including the Sun, where hydrogen nuclei fuse to create helium. The energy generated by fusion reactions exceeds that produced in fission reactions. Example: Fusion reactions in stars, such as the Sun, where hydrogen nuclei combine to form helium.
(b) Graph of Potential Energy between a Pair of Nucleons:
The graph illustrating the relationship between potential energy \( U \) and the separation \( r \) of two nucleons exhibits the following characteristics:
- At extremely short distances (small \( r \)), the potential energy is positive, indicating a repulsive force.
- At an intermediate separation distance, the potential energy reaches its lowest point, signifying a stable configuration characterized by an attractive force.
- As the separation increases further, the potential energy rises, approaching zero as the nucleons become infinitely distant from each other.
The fundamental shape of the graph is depicted below:
\[
\text{Graph of Potential Energy vs Separation (r)}
\]
